System and method for processing ultrasonic signals

ABSTRACT

A system and method for eliminating confusion associated with checking valves, wherein additional test points are added to the measurement of a valve for ensuring the verification of the actual sources of leaks or turbulence. A base line measurement for the valve is established by measuring the level of ultrasonic sound at the two points upstream from the valve. The level of the ultrasound at two downstream points is then measured. The value of the ultrasound at the downstream test points is compared to the values of the ultrasound at the upstream test points. If the values of ultrasound at the downstream test points are higher than the values of the ultrasound at the upstream test points, then the valve is leaking. If the values of the ultrasound at the downstream test points are close to or lower than the values of the ultrasound at the upstream test points, then the valve is not leaking, i.e., the valve is good.

RELATED APPLICATIONS

The present invention is a continuation-in-part which relates to andclaims priority of, U.S. patent application Ser. No. 10/292,799, filedon Nov. 12, 2002, now U.S. Pat. No. 6,707,762 entitled System forHeterodyning an Ultrasonic Signal, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to the field of ultrasonic generatorsand, more particularly, to a system and method for processingheterodyned ultrasonic signals that are generated during valveinspections.

2. Description of the Related Art

It is well known that ultrasonic generators and detectors can be used tolocate leaks or defects, e.g., in pipes. Such a system is shown in U.S.Pat. No. 3,978,915 to Harris. In that arrangement, ultrasonic generatorsare positioned in a chamber through which the pipes pass. At the ends ofthese pipes, exterior to the chamber, ultrasonic detectors are located.At the point where a leak occurs in the pipe or the pipe wall is thin,the ultrasonic energy will enter the pipe from the chamber and travel tothe end of the pipe where the detector is located. The detector willreceive an ultrasonic signal at the end of the pipe indicating theexistence of the leak or weak spot in the pipe.

By locating an ultrasonic generator in a closed chamber, a standing wavepattern with peaks and nodes is established. If a node occurs at theposition of a leak or weak spot, no ultrasonic energy will escape andthe defect will not be detected.

Ultrasonic sensors have also been used to detect ultrasonic energygenerated by friction within mechanical devices as disclosed in U.S.Pat. No. Re. 33,977 to Goodman, et al., the details of which are herebyincorporated herein, in their entirety, by reference. The greater theamount of friction, the greater the intensity of the generatedultrasonic energy. Applying a lubricant to the device reduces frictionand consequently the intensity of the generated ultrasound drops.Measuring ultrasonic energy thus provides a way to determine whenlubrication has reached the friction generating surfaces. Additionally,faulty devices, such as bearings, generate a higher level of ultrasonicenergy than do good bearings and thus, this condition can also bedetected. However, conventional means require two people to perform thisprocedure—one person to apply the lubricant to the device, and oneperson to operate the ultrasonic detector.

In certain instances, e.g., when detecting the malfunction of bearings,an ultrasonic detector is mechanically coupled to the casing of thebearings so that the vibrations caused by the malfunction can bemechanically transmitted to it. With such an arrangement, the frequencyis not set by an ultrasonic generator, but is created by the mechanicalvibration itself. Here, an ultrasonic detector circuit must be capableof sweeping over a band of frequencies to locate the one frequency thatis characteristic of the malfunction. This is usually accomplished by aheterodyning circuit which can be tuned to various frequencies, much inthe manner of a radio receiver.

Since ultrasonic energy used for these purposes is generally in therange of 40 kHz, it is too high in frequency to be heard by a humanbeing. Thus, means are typically provided for heterodyning, or frequencyshifting, the detected signal into the audio range, and various schemesare available for doing this.

Ultrasonic transducers generally produce a low voltage output inresponse to received ultrasonic energy. Thus, it is necessary to amplifythe detected signal using a high-gain preamplifier before it can beaccurately processed. However, if low cost heterodyning and displaycircuitry are to be used, means must be made available to attenuate theamplified signal to prevent saturating these circuits when high inputsignals are present. This attenuation also adjusts the sensitivity ofthe device. For a hand-held unit, the degree of attenuation should beselectable by the user. For example, U.S. Pat. No. 4,785,659 to Rose etal. discloses an ultrasonic leak detector with a variable resistorattenuator used to adjust the output level of an LED bar graph display.However, this attenuation method does not provide a way to establishfixed reference points to allow for repeatable measurements.

U.S. Pat. No. 5,089,997 to Pecukonis discloses an ultrasonic energydetector with an attenuation network positioned after an initialpre-amplifier and before the signal processing circuitry, which createsan audible output and an LED bar graph display. The resistors in thePecukonis attenuation network are designed to provide an exponentialrelationship between the different levels of attenuation. However,Pecukonis does not heterodyne the detected signals to produce an audibleoutput, but rather teaches the benefits of a more complex set ofcircuits which compress a broad range of ultrasonic frequencies into anarrower audible range. For many applications, the cost and complexityof this type of circuitry are not necessary.

When using ultrasonic energy to detect leaks, it is useful to have aportable ultrasonic sensor which indicates the presence and intensity ofultrasonic energy both visually and audibly. U.S. Pat. No. Re. 33,977 toGoodman et al. discloses an ultrasonic sensor that displays theintensity of the detected signal on an output meter operable in eitherlinear or logarithmic mode, and also provides for audio output throughheadphones. U.S. Pat. No. 4,987,769 to Peacock et al. discloses anultrasonic detector that displays the amplitude of the detectedultrasonic signal on a ten-stage logarithmic LED display. However, thedetector disclosed in Peacock does not process the detected signal toproduce an audible response, nor does it provide for signal attenuationafter the initial pre-amplification stage.

Means have been proposed for increasing the output of the ultrasonictransducer. For example, in U.S. Pat. No. 3,374,663 to Morris it issuggested that an increase in the voltage output can be achieved byserially arranging two transducers. It has been found, however, thatwith such an arrangement a typical transistor pre-amplifier loads thetransducers to such an extent that the gains achieved by stacking themserially are lost. The Morris patent proposes the use of a tripleDarlington configuration in order to produce a sufficiently high inputimpedance to prevent this degradation in the signal produced by thestack of transducers. Unfortunately, the transducers in this arrangementare not placed so that they both readily receive ultrasonic energy.Thus, the Morris arrangement is not entirely satisfactory.

SUMMARY OF THE INVENTION

The present invention is directed to providing improved methods andapparatus for detecting leaks and mechanical faults by ultrasonic means.In accordance with the invention, an input transducer signal is appliedto a unity gain buffer amplifier that is used to maintain the impedancelevel seen by the transducer. The processed signal from the unity gainbuffer amplifier is supplied to a voltage control amplifier that alsoreceives a voltage control signal that is generated by adigital-to-analog converter located on an external I/O board. Thevoltage control signal is used to switch the voltage controlledamplifier such that the dynamic range of the signal is expanded prior toa clip of the signal. The voltage control signal is based on a levelthat is programmed into the voltage control amplifier by thedigital-to-analog converter located on the external I/O board. Thevoltage controller is thus controlled by the I/O board in response tocommands sent to the external I/O board from a micro-controller.

The output from the voltage controlled amplifier is connected to a fixedgain differential amplifier. The output signal from the fixed gainamplifier is supplied to a variable gain amplifier that is switchablebetween two fixed levels, such as 0 dB and 20 dB. The gain level of thevariable gain amplifier is toggled between the two fixed gain levelsbased on a level that is determined by the amount of gain that isprogrammed into the voltage control amplifier.

The output of the variable gain amplifier is supplied to a pair ofheterodyning circuits, i.e., a dual heterodyning circuit. At eachrespective heterodyning circuit, the output signal from the variablegain amplifier is multiplied with a local oscillator signal that isinternal to each circuit. Here, each local oscillator is nominally setto 38 kHz such that for a 40 kHz input transducer signal, a differencefrequency of about 2 kHz (i.e., the audio component) is provided at theoutput of each heterodyning circuit.

The output signal from the first heterodyning circuit is amplified anddivided into two signal branches. The first signal branch is transformercoupled to a headphone output. The second signal branch is connected toan amplifier that is also transformer coupled to a line output and alsoapplied to an external audio amplifier. The output from the second ofthe heterodyning circuits is amplified and supplied to a meteringcircuit.

In addition, a further analog signal path is created at the secondheterodyning circuit. The signal in this path is converted to a lineardB format analog signal and supplied to a micro-controller. This analogsignal is converted in the micro-controller into a digital signal by ananalog-to-digital converter, and is further converted in themicro-controller into a WAV file format, as well as other digital signalformats, for subsequent spectral analysis.

The present inventors have determined that a heterodyned signal thatdrives a meter requires a relatively large dynamic range, but a limitedfrequency response, while a heterodyned signal that is required forheadphones or spectral analysis may have a low dynamic range, butrequires high resolution. Further, it has been found that the resolutionor frequency response of the input transducer signal is degraded if asingle heterodyning circuit is used to drive a number of circuits ormeters with competing requirements. In order to overcome these competingrequirements, the present invention uses a dual heterodyning circuit inwhich the two individual heterodyne circuits are separately optimized sothat the second results in a signal with a large dynamic range and thefirst results in a signal with a great resolution, and neither undulyloads the transducer array or obscures subtle frequency components. Thispermits the capture of particularly low level frequency components forextraction during spectral analysis.

In accordance with the invention, the first heterodyning circuit has afeed back loop filter and a transformer to provide an enhanced spectral(i.e., frequency) response. This circuit is used to drive the headphone,a wave file generator and a line output. This signal, which has a modestdynamic range but a high frequency response and a low signal to noiseratio, allows the spectrum of the signal to be analyzed in real time byan external spectrum analyzer, recorded for later analysis or listenedto in real time through the headphones.

The second heterodyning circuit has a smaller frequency response but alarger dynamic range so that it can drive the meter. In accordance withthe invention, the second heterodyne circuit is not required to have anoptimized spectral response. If the meter were driven with the firstheterodyne circuit, the impedance and dynamic range requirements of themeter would adversely affect the response. Thus, two heterodyne circuitsare used, with the circuit that drives the meter being simpler, and lesscostly to manufacture and having a larger dynamic range.

In either mechanical analysis or electrical equipment analysis, a largenumber of frequencies in the low frequency range become lost. This isespecially true in the case of electrical applications. After extendeduse of the detection equipment, operators often tend to begin to usetheir ears as a guide to the condition of an area of concern. However,it is extremely difficult for a person to discern with their ears thedifferences between inputs that are electrical in nature and inputs thatare vibrational. Further, in other technologies, such as vibrationanalysis, infrared technologies, or where rotational equipment is used,the use of the human ear is a highly unreliable way in which to predictfaults. For example, a transformer resonating at 60 Hz may cause acomponent in an equipment cabinet to resonate at the same 60 Hz. When anoperator listens to the cabinet containing the component that isvibrating at the 60 Hz, it is impossible to determine whether theresonance is electrical or mechanical.

Typically, on/off valves are checked for their position, e.g., open orclosed, or for leakage in the closed position. By way of a contactmodule, such valves can be tested using the portable ultrasonic deviceof the present invention. Contact modules are generally used to detectstructure borne ultrasound. Transducers are contained in the module, anda rod is attached to the ultrasonic device. The rod acts as a waveguidethat conducts ultrasound to excite the transducers to generate a signalthat the ultrasonic device can measure.

A high level of confusion occurs when checking valves for leaks or“bypassing” caused by turbulent flows, either upstream or downstreamfrom the valve in question. When measurements are performed at adistance from the valve, confusion can arise because an operator isunable to determine whether the valve is good or bad. This occursbecause the operator is unable to distinguish between problems thatoccur at the remote location and those which occur at the valve itself.In addition, if the user only checks the upstream and downstream sidesof a valve, then confusion may arise because they may believe the valveis “bypassing” and thus, change the valve. A valve is bypassing if fluid(gas or liquid) passes through the valve when it is closed.

If the operator falsely concludes that the downstream reading is higherthan the upstream reading, which is usually indicative of a leakingvalve, the confusion caused can be extensive in terms of the time andcost for replacing a valve that is not defective and is not the sourceof the potential problem. The actual source of the higher reading forthe upstream side of the valve can originate from turbulence generatedfurther down the piping from the valve, such as from turbulence causedby a right angle connection or even from a partial blockage of the pipe.The method of the present invention eliminates such confusion associatedwith checking valves by adding additional test points with which toensure verification of the actual source of leaks or turbulence.

In accordance with the method of the invention, this is achieved byestablishing a base line measurement for each valve under test. Theultrasonic sound at multiple points upstream and downstream from thevalve is measured. In the preferred embodiment, the ultrasonic sound attwo upstream points and two downstream points is measured. Prior toperforming all measurements, a visual inspection of the valve isperformed to confirm that the valve is closed or in the off position.

The measurement of the ultrasonic sound at the first upstream point isthen made at a distance located X times the pipe diameter from thevalve. The measurement of the ultrasonic sound at the second upstreampoint is made at a point located directly upstream of the valve,approximately at the pipe fitting. The two downstream measurement pointsare at a distance of equal relationship to the upstream test point,i.e., the first downstream measurement point is located at a distancelocated X times the pipe diameter from the valve, and the seconddownstream measurement point is located directly downstream of thevalve, approximately at the pipe fitting. In the preferred embodiment, Xis six (6), i.e., the first measurements are located at a point that is6 times the diameter of the pipe away from the valve.

While touching the contact module to a measurement point to measure theultrasonic energy at the two upstream points, the sensitivity of thedual heterodyning circuit is adjusted by turning a rotary knob on therear of the portable device so that a liquid crystal display, also onthe rear of the portable ultrasonic device, displays the dB value of theultrasonic measurements. These initial upstream ultrasound valuesestablish baseline measurements for the valve. The value of theultrasonic sound at the first and second upstream points should be closeto each other. In some circumstances, the second measured ultrasonicvalue can be slightly lower than the first measured ultrasonic value. Incontemplated embodiments, the second measurement is performed withoutre-adjusting the sensitivity of the dual heterodyne circuit.

The level of the ultrasound at the two downstream points is thenmeasured. The value of the ultrasound at the first downstream test pointis compared to the values of the ultrasound at the upstream test points.The value of the ultrasound at the second downstream test point ismeasured to ensure that no ultrasonic sound is emanating downstream fromthe valve. If the value of the ultrasonic sound measured at the seconddownstream point is greater than the value of the ultrasonic soundmeasured at the first downstream point, then this ultrasonic sound mustbe “tuned out” or “shut off” to obtain a proper test of the valve. Whenit is not possible to tune out or shut off a downstream structure borneultrasound, it is necessary to locate the source of the highest readingto determine its effect on the outcome of the measurements.

In accordance with the embodiments of the invention, additionalultrasound measurements further downstream are performed to assist inlocating/confirming the source of the ultrasound. Hence, if the valuesof the ultrasound at the downstream points are higher than the values ofthe ultrasound at the upstream points, the valve is leaking. On theother hand, if the values of the ultrasound at the downstream points areclose to or lower the values of the ultrasound at the upstream points,then the valve is not leaking, i.e., the valve is good.

By using the dual heterodyning circuit of the present invention toprovide the enhanced spectrum, it becomes clear whether a detectedresonance is mechanical or electrical. In addition, fault frequenciesare also more easily discernible. In other words, the enhanced signaloutput provides a lower signal-to-noise ratio, so as to increase theease with which frequency components are analyzed. In addition, themethod of the invention eliminates the unnecessary replacements of“good” valves, which can be expensive in certain environments, such asin a nuclear plant or on a ship, where the valves are welded into place.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages and features of the invention willbecome more apparent from the detailed description of the exemplaryembodiments of the invention given below with reference to theaccompanying drawings in which:

FIGS. 1A-1 and 1A-2 form an exemplary block diagram of the dualheterodyning circuit in accordance with the present invention;

FIGS. 2A-1 through 2K-2 form a schematic diagram of the dualheterodyning circuit shown in FIGS. 1A-1 and 1A-2;

FIG. 3A through FIG. 3B-9 form a block diagram of the I/O board, themicro-controller, and the rear panel in accordance with the invention;

FIG. 4 is a block diagram illustrating a flash card inserted into themicro-controller of FIG. 3(a);

FIG. 5 is a bottom view of the ultrasonic instrument of the presentinvention;

FIG. 6 is a perspective view showing the flash card and rear panel ofthe ultrasonic instrument of the invention;

FIG. 7 is a plan view of the rear panel of the ultrasonic instrument ofthe invention;

FIG. 8 is a front view of the ultrasonic instrument of the invention;

FIGS. 9(a) and 9(b) are block diagrams of an additional aspect of theinvention;

FIG. 10. is an illustration of an exemplary network of piping in whichthe method of the invention is implemented; and

FIGS. 11(a), 11(b) and 11(c) are a flow chart illustrating the steps ofthe method of the invention.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

FIG. 6 is a perspective view of a portable ultrasonic detector 600.Toward the front of the housing there are ultrasonic transducers 95, asshown in FIG. 8. Micro-processor controlled circuits for heterodyningthe ultrasonic signal to shift its frequency to the audio range arecontained in the body of the housing. A display 82 is located at theback so the operation and the results can be viewed. At the back, thereis also a jack 88 for headphones, so that the user can listen to theaudio sound during a test, e.g., as a way of locating a leak. Otherjacks and controls are located on the body or will be describedsubsequently.

FIGS. 1A-1 and 1A-2 form an exemplary block diagram of the dualheterodyning circuit in accordance with the present invention which islocated in the housing of the ultrasonic detector. In FIG. 1A-1, aninput signal is applied from an ultrasonic transducer to a bufferamplifier 12(U4B) at input 11(P10). Typically, unity gain buffer 12 isused to maintain at a desired level the impedance level seen by thetransducer. The processed signal from buffer 12 is supplied to voltagecontrolled amplifier (VGA) 14 (U5) that also receives a voltage controlsignal 15 that is generated by a digital-to-analog converter on anexternal I/O board shown in FIGS. 3A thru 3B-9. The voltage control isthus controlled by the I/O board in response to commands sent to theexternal I/O board from a micro-controller (see FIGS. 3A thru 3A-10).

Voltage controlled amplifier 14 is connected to a fixed gain amplifier16. In preferred embodiments, amplifier 16 has a fixed gain ofapproximately 20 dB. The output signal from amplifier 16 is supplied tovariable gain amplifier 18 (VGA) that is switchable between two fixedlevels, such as 0 dB and 20 dB. The gain level of amplifier 18 istoggled between the two fixed gain levels based on a signal levelapplied to input 17. This signal is determined at the micro-controlleron the I/O board based on the amount of gain that is programmed into thevoltage controlled amplifier 14.

The output of VGA 18 is supplied to a first heterodyning circuit 20(U8). In heterodyne circuit 20, the output signal supplied to VGA 18 ismultiplied in multiplier 22 by a local oscillator 21 that is internal toheterodyne circuit 20. Sum and difference frequencies are provided atthe output of circuit 20. At this point, the high frequency componentsof the signal are filtered out and a difference signal is buffered inamplifier 24, such that an audio signal is provided. The localoscillator 21 within circuit 20 is nominally set to 38 kHz such that fora 40 kHz input transducer signal, a difference frequency isapproximately 2 kHz. Amplifier 24 is used to amplify the output signaland apply it to terminal 23 which leads to a metering circuit (notshown). This signal has a large dynamic range.

The output signal from VGA 18 is also received by amplifier 30, whichamplifies this signal prior to supplying it to a second heterodyningcircuit 32. In exemplary embodiments, the signal supplied to amplifier30 is amplified by approximately 10 dB. The second heterodyne circuit 32receives the output of amplifier 30 and multiplies this signal inmultiplier 33 by a local oscillator 34 that is also internal to circuit32. Sum and difference frequencies are created at the output ofheterodyne circuit 43. The high frequency components of the signal arefiltered out and the low frequency signal is buffered in amplifier 35,such that an audio signal is provided. The local oscillator withincircuit 32 is nominally set to 38 kHz such that for a 40 kHz inputtransducer signal, a difference frequency audio signal is approximately2 kHz. The audio signal is then buffered by a unity gain amplifier 36.The output of amplifier 36 is next provided to an amplifier 37. Inpreferred embodiments, the signal level supplied to amplifier 37 isincreased by approximately 40 dB.

In accordance with the invention, the second heterodyning circuit 32 hasa feed back loop 31 from the output of amplifier 35 to the input ofcircuit 32. This feedback loop 31 provides an enhanced spectral (i.e.,frequency) response.

The output signal from unity gain amplifier 36 is divided into twosignal branches. The first branch leads to the amplifier 37. The secondbranch leads from unity amplifier 36 to amplifier 40 that is coupled toa headphone output by way of transformer 41. In the first signal branch,amplifier 37 is coupled to transformer 39, which in turn is coupled to aline output. The line output is subsequently applied to an audioamplifier (not shown). In addition, a further analog signal fromamplifier 37 is coupled to amplifier 38, where it is attenuated byapproximately −3 dB. The attenuated signal is then supplied to themicro-controller (not shown). This analog signal is converted in themicro-controller into a digital signal by an analog-to-digitalconverter, and is further converted in the micro-controller into a WAVfile format, as well as other digital signal formats for storage andplayback, and for subsequent spectral analysis.

The wideband, high resolution signal from amplifier 36, which is aresult of feedback loop 31, is used to drive the headphone, a wave filegenerator and a line output. This signal, which has a modest dynamicrange but a high frequency response and a low signal to noise ratio,allows the spectrum of the signal to be analyzed in real time by anexternal spectrum analyzer, recorded for later analysis or listened toin real time through the headphones.

The first heterodyning circuit 20 has a smaller frequency response but alarger dynamic range so that it can drive the meter. In accordance withthe invention, the first heterodyne circuit is not required to have anoptimized spectral response. If the meter is driven with the sameheterodyne circuit as the headphone circuit, the impedance and dynamicrange requirements of the meter would adversely affect the headphoneresponse. Thus, two heterodyne circuits 20, 32 are used, with thecircuit that drives the meter being simpler, less costly to manufactureand having a greater dynamic range. The circuit that drives theheadphones has a smaller and a lower signal-to-noise ratio, whichprovides a better spectral response.

By way of example, FIGS. 2A-1 thru 2K-2 Form an exemplary schematicdiagram of the dual heterodyning circuit in accordance with the presentinvention. Buffer amplifier 12 is shown in FIG. 2A-1. A transducersignal having a frequency of approximately 40 kHz±5 kHz is applied viaconnector 11 (P10) by way of capacitors 210 (C27) and 211 (C21),resistors 212 (R20) and 213 (R27), diodes 214 (D2) and 215 (D3) to thebuffer amplifier 12, which is used to maintain the impedance level seenby an input transducer (not shown) at a predetermined fixed level.Typically, amplifier 12 is a standard Integrated Circuit (IC), such asan OP-284ES.

The voltage divider comprising resistors 220 (R36) and 221 (R45), alongwith capacitor 222 (C41) are coupled to the positive input of amplifier44 (U10) that is used to generate a 6 volt low impedance output based onthe 12 volt input that is applied to resistor 220. The 6 volt lowimpedance output is used to provide a reference level for the analogcircuitry of the invention. Amplifier 44 has a feed back loop comprisedof capacitor 222 (C25) and resistor 223 (R33) to improve its response.This amplifier is typically a standard “off-the-shelf” IC, such as anAD797 manufactured by Analog Devices.

Capacitor 230 (C19) and resistor 232 (R24) are connected in series fromthe output of amplifier 12 to the input of voltage controlled amplifier(VCA) 14 (U5). Amplifier 14 with capacitors 234 (C24), 236 (C14), 238(C33), resistors 240 (R21), 242 (R30) provide expanding the dynamicrange of the signal prior to clipping of the signal. Preferably, VGA 14is a standard voltage controlled amplifier, such as a SSM2018Tmanufactured by Analog Devices. The control voltage on pin 11 of VCA 14is generated by a digital-to-analog convertor 71 (DAC) that resides onan I/O board (shown in FIG. 3B-3) that is controlled by an externalmicro-controller (shown in FIGS. 3A-1 thru 3A-10). VOS 302 is thecontrol signal (FIGS. 1A-1). The output of VGA 14 is on pin 3 throughcapacitor 236 and resistor 240 (TP5).

As shown in FIG. 2A-2 and 2B, the output of VCA 14 on TP5 is applied tothe input of the differential amplifier 16 through capacitor 242 andresistor 244. A feed back loop of capacitor 246 and resistor 248 isconnected around amplifier 16. Capacitor 249 and resistors 245, 247 formthe rest of the differential amplifier 16. Amplifier 16 has apredetermined fixed gain level and because of its high common moderejection ratio noise is reduced. The output signal from amplifier 16 iscoupled to the input of variable gain amplifier 18 by way of capacitorC18 and resister R23. In preferred embodiments, amplifier 16 istypically a standard “off-the-shelf” IC, such as an OP-284ES, and has again level of approximately 20 dB.

Amplifier 18 is switchable between two gain levels based on thesensitivity level required by VCA 14. In preferred embodiments,amplifier 18 is switched between 0 dB and 20 dB by an analog switch 45(U3) that is typically a standard “off-the-shelf” IC, such as a DG419DY.Resistor 254 (R19), resistor 256 (R15) and variable resistor 258 (VR1)set the gain, while resistor 260 when shorted across the other resistorby switch U3 sets the second gain level. The output of amplifier 18 isconnected through capacitor 262 (C20) to the output at TP3. This levelis biased by a voltage from variable resistor 264 (VR2).

The micro-controller sets the digital bits DAC, CLK, DACSDO, DACLD onconnector J3 (FIG. 3A-8). These bits are applied to DAC 71 (FIG. 3B-3),which in turn produces the control voltage 302 (VOS or VOF) on J13. Acontrol voltage 302 VOS is received on P13 (FIG. 2H-2). As shown in FIG.2G-2, VOS is then supplied to amplifier 52 (U11A) by way of resistors270 (R57) and 272 (R58) to amplifier 57 by way of resistor 274 (R83).The output of amplifier 52 is provided to one input of differentialamplifier 53. A unity gain buffer amplifier 55 has an input voltage fromvariable resistor 276 (VR7). Its output is applied to the other input ofamplifier 53 as a reference voltage. The output of amplifier 53 isamplified in amplifier 54 and provides the signal at TP12. In effect,the amplifiers 52, 53, 54 and 55 scale and level shift the VOS signal.As can be seen from FIG. 2A-2, the TP12 signal is applied to the controloutput of VCA 14.

The VOS signal level is from approximately 0 to 5 volts. In preferredembodiments, the signal level of VOS is from 0 to 4.095 volts.

In alternative embodiments, variable resistor 280 (VR8) RT1, and RG1(FIG. 2G-2) are optionally connected for providing nominal temperaturecompensation of the system.

Amplifier 57, which also receives the VOS signal, buffers that signaland feeds the positive input (pin 3) of amplifier 56 (U14A) throughresistor 284 (R82), where amplifier 56 is connected in a comparatorarrangement. Here, resistor 286 (R84) is used to provide hysteresis fornoise rejection. Coupled to the negative input (pin 2) of amplifier 56is a variable reference level that is created by variable resister 288(VR9), which sets a reference level. Typically, amplifiers 52, 53, 54and 55 are standard “off-the-shelf” ICs, such as a LM6134AIM.

In accordance with the invention, the reference level that is applied tothe negative input (pin 2) of amplifier 56 is set during a calibrationprocess to generate a CLIP signal that is output from pin 1 of amplifier56. This CLIP signal is used to switch the variable gain amplifier 18from 0 dB to +20 dBs. (See the input switch to switch 45 on FIG. 2B.)Simultaneously, the gain of the transducer pre-amps (not shown) isdecreased by 20 dB. Of note, in order to extend the dynamic range of thetransducer amplifier (not shown), the overall gain of the system plusthe transducer pre-amp must have no net increase in gain. As a result,if the variable gain amplifier in the pre-amp located within thetransducer has a 100 dB dynamic range and a pad of 20 dB is inserted,then a clean, un-clipped dynamic range of 120 dB is achieved from theentire system. The signal that controls the switching of amplifier 18 isthe CLIP signal that is generated by amplifier 56.

Amplifier 56 is controlled by a sensitivity setting such that theoverall sensitivity of the system is determined by the micro-controllerwhereby an operator using a controller 72 on a front panel of theinstrument 600 can adjust the overall sensitivity (see FIG. 5 and FIG.7). As a result, if the sensitivity of the system is lowered by apredetermined level, the clip signal output from amplifier 56 is toggledsuch that gain switching occurs at the transducer pre-amp and atvariable gain amplifier 18. In preferred embodiments, the predeterminedlevel is 10 dB downward from the maximum sensitivity of the system.

With reference to FIG. 2A, differential amplifier 43 (U4A) receives theoutput 268B of variable gain amplifier 18 (FIG. 2B) on its positiveinput 241 (pin 3). This signal is received through resistors 251 (R13)and 253 (R17), and capacitor 255 (C10). The output of amplifier 43 isconnected to zener diode 259 (D1) at TP1. Amplifier 43 functions as apositive rectifier circuit outputting a positive DC voltage proportionalto the amplitude of the signal. Zener diode D1 clamps the output ofamplifier 43 to a voltage of approximately 5 volts to prevent themicro-controller from being subjected to excessive voltage levels. As aresult, a DC voltage is generated which the micro-controller compares toa predetermined value. If the DC voltage is greater than thepredetermined value then the micro-controller indicates saturation onthe LCD display by displaying an over range condition.

The output of amplifier 18 is also applied to the first of a pair offunction generator circuits that form the dual heterodyne circuits 20(U8), 32 (U99), as shown in FIGS. 2F-1 and 2F-2. The output of amplifier18 is further connected to resistor 130 (R8) that is connected in serieswith capacitor 135 (C5), which is subsequently connected to the base oftransistor 134 (Q1) (FIG. 2C). The collector of transistor 134 iscapacitively connected to the input (pin 1) of the second of the pair offunction generator circuits, i.e., heterodyne circuit 32 (U99) (see FIG.2F-2) by way of capacitor 136 (C3). As shown in FIG. 2C, a feed backloop comprising capacitors 140 (C12), 142 (C11), transistor 47 (Q2) andvariable resistor 144 (VR14) provides a feedback signal at pin 1 offunction generator (heterodyne) circuit 32 (see FIG. 2F-2). Inaccordance with the invention, transistor 46 amplifies the output signalfrom amplifier 18 by a predetermined amount. In the preferredembodiment, the predetermined amount is 10 dB.

Ultrasonic signals leaking from a container (not shown) are detected bythe transducer (not shown), amplified and frequency shifted such that auser is provided with an indication of the existence of a leak by way ofthe sound heard in a pair of headphones (see FIG. 2K-2). The actualfrequency shift of the ultrasonic signal is accomplished in the functiongenerator 32. The generator (FIG. 2F-1) may be a commercially-availableintegrated circuit, such as the EXAR 2206, which has been wired toproduce sine wave outputs at a frequency determined by tuning resistor180 (VR3) connected to pin 7 of circuit 32, resistors 181 (R46) and 182(R49) connected from pins 15 and 16 to ground, capacitors 183(C38), 184(C43), and resistor 186 (R52). One characteristic of circuit 32 is thata particular bias applied to its input (pin 1) will cause it to producean amplitude-modulated (AM), suppressed-carrier output. The bias toobtain this suppressed-carrier modulation is derived from variableresistor 144 (VR14) (FIG. 2C). If capacitor 183 (C37) and resistor 180(VR3) are selected to produce a carrier signal that differs from theultrasonic signal by a frequency in the audio band, the output ofheterodyne circuit 32 will be an audio signal related to the inputultrasonic signal and a much higher signal. In particular, the outputsignal will be equivalent to the sum and difference frequencies of theultrasonic signal and the carrier signal generated within circuit 32,but the carrier signal itself will not be present in the output. If forexample, variable resistor 180 (VR3) is set such that circuit 32generates a 42 kHz signal and the ultrasonic signal applied throughcapacitors C3 to circuit 32 is at 40 kHz, the output will be at 2 kHzand at 82 kHz. In preferred embodiments, the oscillator in circuit 32 isadjusted between a range of 20 kHz and 100 kHz.

Although a proper bias on the input to circuit 32 will eliminate orsuppress the carrier generated by that circuit, it has been found thatthis adjustment is critical and some carrier may leak through due totemperature and voltage variations. Also, as the carrier frequency ischanged due to changes in the setting of resistor 180 (VR3), there arechanges in the circuit operation that may cause the carrier to appear inthe output unless there is an adjustment of the bias. In order toprovide this adjustment, a servo or feedback network is provided.

In particular, the output of circuit 32 is also capacitively coupled tothe base of transistor 35 (Q3) by way of capacitor 190 (C36), andresistor 192 (R40), as shown in FIG. 2F-2. these components provide aninput signal for the feedback network formed by transistor 47 thatbiases pin 1 of circuit 32 (see FIG. 2C). Here, transistor 35 providesamplification of the output signal from pin 2 of circuit 32 by apredetermined amount. In preferred embodiments, the predetermined amountof amplification is 40 dB.

The output from pin 2 of circuit 32 is also fed to voltage amplifier 36(FIG. 2E), where the signal from pin 2 is buffered. By way of resistor171 (R140), the output signal from amplifier 36 feeds the base oftransistor 37 (Q6) over line 304, by way of capacitor 305 (C66) (FIG.2I-1). Here, the output signal from amplifier 36 is coupled totransformer 39 to thereby generate a low frequency output (“LFO”). Theaudio signal on line 304 is also applied to summing amplifier 68 (FIG.2K-2) which in turn drives amplifier 40. Amplifier 40 drives transformer41 which is used to power the headphones. In preferred embodiments ofthe invention, transformer 39 has a turns ratio of approximately 1:0.05,and the output signal is used to drive low impedance loads. Thetransformer 41 has a turns ratio of 1:0.175.

The output signal from amplifier 36 (FIG. 2E) is also provided toamplifier 50, where it is attenuated by approximately −3 dB, based onresistors 300 (R34) and 302 (R26). Amplifier 50 (U1B) and amplifier 36are typically standard “off-the-shelf” ICs, such as an OP-284ES. Theoutput from amplifier 50 is supplied to the micro-controller forconversion into a digital signal by an analog-to-digital converterlocated in the micro-controller (not shown). This digital signal isconverted into a digital format, such as a WAV file, for subsequentimage processing.

Signals VR and +12VR are applied from a power supply (FIG. 2K-1) to thecircuit of FIGS. 2I-1 and 2I-2. These signals are applied to thenegative and positive terminals of differential amplifier 59 (U12B).Capacitor 306 (C48) and resistor 308 (R70) are connected to form afeedback loop about amplifier 59. The signal +12VR is applied to thepositive input of amplifier 59 through resistors 310, 311 and 312 (R81).A zener diode 314 (D5) is connected between resistors 310 and 311. VR isconnected to the negative input of amplifier 59 through resisters 315(R68) and 316 (R69). The output of amplifier 59 is connected to zenerdiode 318 (D4), and through resister 319 (R76) to the positive input ofamplifier 60 (U12A). A variable resistor 320 (VR6) is connected toamplifier 60 and serves to establish a reference point of amplifier 60.

Signal +12V1 is applied from the power supply (FIG. 2K-1) to the biasamplifier shown in FIG. 2D. This 12V signal is applied to the VINterminal of voltage regulator 48 (U2). The output (VOUT) of voltageregulator 48 provides a +5 volt TTL signal that is supplied to amplifier49 (U1A) by way of resistors 360 (R6), 362 (R9), and capacitors 364 (C7)and 365 (C8). Amplifier 49 provides a regulated +2.5V voltage that isused as a reference voltage in accordance with the invention. The +5Vvoltage is also used to provide a TTL reference level to all othercircuit ICs where required.

With further reference to FIG. 2I-2, amplifiers 59 and 60 provide acomparator circuit that generates a low battery monitor. By way of zenerdiode D5, a regulated reference voltage is generated and applied to thepositive input (pin 5) of amplifier 59. Concurrently with application ofthe regulated reference voltage, a battery voltage is applied to theresistive divider (315, 311) on the negative side (pin 6) of amplifier59. The reference voltage at zener diode D5 remains relatively constantdue to the clamping action of the zener diode D5.

Zener diode D4 in FIG. 2I-2 is connected to the output of amplifier 59,and clamps the output voltage to approximately 5 volts such that themicro-controller is not subjected to excessive voltage levels. If thebattery voltage falls below a predetermined level, then the inputvoltage at the negative input of amplifier 59 will also fall below thereference level. In accordance with the invention, the output ofamplifier 59 is zero to indicate a fully charged battery, andapproximately 3.5 volts to 4 volts (nominal) to indicate that thebattery capacity is low and needs to be recharged. The output ofamplifier 59 is inverted in amplifier 60 and produces the OFF signalused in the circuit of FIGS. 2H-1 and 2H-2 as will be explainedsubsequently. As a result, a means is provided for the micro-controllerto indicate on an LCD whether or not the battery is adequately charged.In preferred embodiments, amplifiers U12A and U12B are standard“off-the-shelf” ICs, such as an LM6132.

In the contemplated embodiments of the invention, the LCD is a screenthat is large so that the display can easily be seen by the operator. Inaccordance with the contemplated embodiments, this would include a timeseries display of the heterodyned ultrasonic signal to permit theviewing of measurement trends in real time.

Returning to FIG. 2E, when the battery level falls below the optimumoperating level, the base of transistor 73 (Q4) is pulled high by theoutput of amplifier 60 (FIG. 2I-I) online 322. This causes the plusinput of amplifier 36 to be low. As a result, the output signal fromamplifier 50 is also low.

As stated previously in connection with FIG. 1A-1, the first output fromamplifier 18 is applied to the first of the pair of function generatorcircuits, e.g., circuit 20 (see FIG. 2F-1). This generator may also be acommercially available integrated circuit, such as the EXAR 2206, whichhas also been wired to produce sine wave outputs at a frequencydetermined by tuning resistor 330 (VR5) connected to pin 7 of thecircuit 20, resistor 331 (R51), capacitor 332 (C42), as well ascapacitor 333 (C37) connected between pins 5 and 6, and resistors 334(R43) and 335 (R48) connected to ground from pins 15, 16 of circuit 20.

Function generator circuit 20 multiples the first output signal using anoscillator that is internal to circuit 20. In a manner similar tocircuit 32, the sum and difference frequencies of the ultrasonic signalare also generated at the output pin 2 of circuit 20. In preferredembodiments, the local oscillators in circuit 20 and circuit 32 arenominally set to 38 kHz. As with the tuning resistor 180 (VR3) that isconnected to circuit 32, if tuning resistor 330 (VR5) is set such thatcircuit 20 generates a 42 kHz signal and the ultrasonic signal appliedis at 40 kHz, the output at pin 2 of circuit 20 will be at 2 kHz and at82 kHz. Since only the audio band signal is desired, the filter circuitcomprising resistors R38, R39, R42 and R44, capacitors C35, C40 and C39will eliminate the 82 kHz sum signal. In preferred embodiments theoscillator in circuit 20 is adjusted between a range of 20 kHz and 100kHz.

Frequency control of function generator circuits 20 and 32 is achievedby the micro-controller 80 (see FIGS. 3A thru 3B-9). As shown in FIG.2F-1, an input signal 302 VOF is applied to the positive input (pin 5)of amplifier 51 (U7B). VOF 302 originates from the DAC 71 which is onthe I/O board (FIG. 3B-3). The voltage level of VOF is fromapproximately 0 to 4.095 volts. The oscillation frequency of circuit 20and circuit 32 is set during a calibration process by way of variableresistors 330 (VR5) and 180 (VR3) (see FIGS. 2F-1 and 2F-2). Inaccordance with the invention, when the frequency of the system istuned, voltage VOF is changed, i.e., the voltage applied to pin 5 ofamplifier 51 is changed (FIG. 2F-1). As a result, the frequency of thelocal oscillators of circuit 20 and circuit 32 can be changed in therange from approximately 20 kHz to 100 kHz.

In accordance with the invention, the output from heterodyne circuit 20(FIG. 2F-1) is provided to amplifier 24 on line 340, as shown in FIG.2H-1. Connected to amplifier 24 are resistors 345 (R73), 344 (R65), andcapacitors 342 (C47), and 346 (C53). The output signal meter (pin 1) ofamplifier 24 is provided to an additional circuit for conversion intoRMS units and dB units (see FIGS. 2J-1 thru FIG. 2J-3). The collector oftransistor 74 (Q5) (FIG. 2H-1) is connected to the positive input ofamplifier 24, while the base of transistor 74 is connected throughresistor 348 (R80) to OFF signal output from amplifier 60 FIG. 2I-2). Asa result, when the battery level falls below the optimum operatinglevel, the base of transistor 74 is pulled high and the output signalfrom amplifier 24 is terminated. Typically, amplifier 24 is a standard“off-the-shelf” IC, such has an OP-284ES.

The output signal meter (pin 1) of amplifier 24 shown in FIG. 2H-1 isprovided to the input of amplifier 61 (U9B) by way of connector J11(FIG. 2J-1). Connected to the positive input (pin 5) of amplifier 61 areresistors 400 (R106) and 405 (R107). A low pass filtered output signalfrom amplifier 61 is provided to the positive input (pin 3) of amplifier62 (U9A) through capacitor 411 (C74) where it is buffered and outputfrom pin 1 of amplifier 62 over resistor 420 (R105) and capacitor 423(C72) to pin 15 of RMS-to-DC convertor 65 (U19). Typically, amplifiers61 and 62 are standard ICs, such as an OP-284-ES. RMS-to-DC convertor 65is typically a standard “off-the-shelf” IC, such as an AD637manufactured by Analog Devices.

With further reference to FIG. 2J-2 RMS-to-DC convertor 65 computes theroot-mean-square, or the mean square of the absolute value of the inputsignal at pin 15 of converter 65 and provides an equivalent dc outputvoltage at pin 16, as well as an RMS output at pin 11. The DC outputvoltage at pin 16 of converter 65 varies linearly to the dB level of theinput signal's amplitude at pin 15 of converter 65. Here, the dc outputvoltage is a buffered output that is provided to amplifier 67 (U17A) byway of resistor 426 (R110) and resistor temperature compensator 429(RT1).

Resistors 432 (R111), 435 (R108) and variable resistor 438 (VR10) arecoupled to amplifier 67. Together, these resistors control the gain ofamplifier 67 to thereby scale the dB level of the output signal that isseen on connector J11. Here, R108 is not installed so VR10 completelycontrols the scaling of the dB output signal from amplifier 67. Thisoutput signal is forwarded by way of pin 1 (TP21) on connector J11 tothe I/O board shown in FIGS. 3B thru 3B-9 and the micro-controller shownin FIG. 3A thru FIG. 3A-10.

As further shown in FIG. 2J-2 voltage regulator 64 (U20) is connected toBUFIN (pin 1) of the RMS-to-DC convertor 65. The voltage regulator 64receives +12V2 that is supplied on connector J11 from the power supply(FIG. 2K-1) and converts this 12 volt input voltage to a regulatedoutput voltage that is output on pin 2 of regulator 64. Resistors 441(R113), 444 (R113), and 447 (R112) set the level of a regulated outputvoltage from regulator 64, where variable resistor 450 (VR11) provides ameans to adjust the output current and set the 0 dB reference level forconverter 65 of this regulator. Typically, the voltage regulator 64 is astandard “off-the-shelf” IC, such as a LM317 manufactured by NationalSemiconductor Corporation.

Coupled to output offset (pin 4) and analog common (pin 3) of theRMS-to-DC convertor 65 is a voltage regulator 66 (U21) that alsoreceives the +12V2 voltage from the power supply. The voltage regulator66 provides a +5 volt output that is also supplied to the positive input(pin 3) of amplifier 67. Voltage regulator 66 is typically a standard“off-the-shelf” IC, such as a LM78L05CM.

RMS output (pin 11) of the RMS-to-DC convertor 65 is provided to thepositive input (pin 5) of amplifier 63 through resistor 453 (R102).Averaging capacitor 464 (C75) is connected across pins 11 and 10 ofconvertor 65 and is used to determine the averaging error that occursduring the calculation of the true RMS of the input signal supplied topin 15 of the convertor 65. The magnitude of the error is dependent onthe value of capacitor 464. As shown in FIG. 2J-3, the RMS output frompin 7 of amplifier 63 is forwarded by way of pin 2 of connector J11 tothe I/O board shown in FIG. 3(b) and the micro-controller shown in FIG.3(a). Typically amplifiers 63 and 67 are standard “off-the-shelf” ICs,such as a LM6132AIM.

The dB output signal at J11 pin 1 (FIG. 2J-1) has a 50 dB dynamic range,a 0-5V DC scale for direct input to the micro-controller, and anaccurate linear dB format. These provide an elimination of the need forexpensive DSP processors or math co-processors, a limitation orreduction of the memory requirements for data and code, and because ofthe accurate analog preprocessing, an elimination of the need forelaborate signal analysis or data conversion algorithms. In addition, areduction of signal processing time is also provided, as well as reducedprocessor clock speeds which in turn lowers power consumption. It shouldbe noted that this invention performs real time analog signal processingon the heterodyned signal only.

Turning now to FIG. 2K-2, therein shown is an audio amplifier that isused to provide an audio output signal that is supplied to a pair ofheadphones connected to the jack 88 (J12) on the rear panel of thehousing (FIG. 7).

As stated previously, the audio signal on line 304 is applied to oneinput of the inputs of the summing amplifier 68. An input alarm signalis supplied to the second input of the summing amplifier throughcapacitor 509 (C62), resistors 500 (R90), 503 (R91), and variableresistor 506 (VR15). Voltage follower amplifier 69 (U15A) utilizes the+12V voltage from the power supply to create a 6 volt reference level(pin 1) that is supplied to the positive input (pin 5) of summingamplifier 68.

The output signal from the summing amplifier 68 is applied to audioamplifier 40 (U16) which is transformer coupled by transformer 41 (T1)to the jack 88 on the rear panel of the housing (FIG. 7). Control of theaudio volume is achieved by a signal VOL that is provided on connectorJ7 through resistors 518 (R96), 521 (R97) to pin 4 of amplifier 40. Inpreferred embodiments, amplifier 40 is a standard “off-the-shelf” IC,such as a TDA7052A manufactured by Philips Semiconductors.

FIGS. 9(a) and 9(b) are block diagrams of an additional aspect of theinvention. In FIG. 9(b), a digital camera 90 is used to make a pictureof the device being ultrasonically measured. The camera 90 is typicallymounted on the detector housing (FIG. 9(a)). The picture signal and thesignal from the dual heterodyne circuit may be combined in a circuit 75,but the camera may be activated independently of the system. Thecombiner 75 may be connected to a printer 76 and transmits printinformation directly to the printer from a user in a manner that isknown. In preferred embodiments, the camera is a digital camera thatstores image files. Thus, pictures of the device under test may beprinted, as well as text results.

In certain embodiments, the camera utilizes a laser beam to pinpoint thelocation of the image. The recorded image is then “coupled” or “linked”to the stored information for that location, e.g., ultrasonic data, WAVfile, and atmospheric conditions. The recorded image and the storedinformation for the image location is then uploaded to a suitableportable storage device in the instrument, such as a flash card 83 (FIG.4 and FIG. 6), smart media or memory stick. The recorded image and thestored information is then downloaded to a data base computer andincorporated into a data base program that generates a report fordetermining the condition of the device being measured.

With specific reference to FIG. 9(b), when an ultrasonic measurement ofa device is performed, a picture can be captured and stored in memoryusing the camera 77. The picture can then be forwarded tomicro-controller 80 where it is combined with the WAV and line outputfrom the second heterodyne circuit 32 (see FIG. 2F-1) in combiner 75 foroutput to the printer 76. In preferred embodiments, the printoutcomprises a spectral display of the line output and a graphical displayof the WAV file information from the second heterodyne circuit 32 (seeFIG. 2F-1), as well as a picture of the device under test.

With reference to FIG. 3A-1, sensitivity encoder 100 is used to increaseor decrease the sensitivity level of the dual heterodyne circuit inaccordance with the present invention. As shown in FIGS. 6 and 7, thesensitivity is adjusted by turning a rotational knob 72 that is locatedat the back of the housing. In preferred embodiments, the sensitivityencoder 100 is a rotational optical encoder.

Rotation of the sensitivity encoder 100 by way of knob 72 changes asignal on P24 (FIG. 3B-5 which causes D/A converter 71 to the change theoutput level of the control voltage VOS 302 on connector J13 (FIG. 3B-8)that controls the gain of VCA 14 (see FIG. 2A-2). Consequently, changesin the gain of VGA 14 produce proportional changes in the sensitivitylevel of the dual heterodyne circuit.

With reference to FIG. 7, LCD 82 provides a display of data that is usedto distinguish between trends or deviations in readings. As a result, auser is provided with the means to bypass valve analysis and pinpoint anultrasonic source, such as an internal leak in a tank or vessel, or anunderground leak in gas piping or electrical transmission lines.

Sensitivity level indicator 105, shown on the LCD 82, provides the userwith the ability to view the sensitivity level setting of the dualheterodyne circuit. As a result, the user can consistently set thesensitivity level of the circuit to permit repeated comparativefrequency spectrum measurements, where repeatability is critical. Asshown in FIG. 7, LCD 82 displays the sensitivity level setting as arange of integer numbers. In the preferred embodiment, this range isfrom 0 to 70, where S is an abbreviation for sensitivity.

In accordance with the invention, the integer numbers represent theadjustment range of VGA 14 (FIG. 2A-2), where each integer valuecorresponds to one decibel in the change of the gain of VGA 14. Inaccordance with the preferred embodiment, a sensitivity level setting of70 corresponds to maximum sensitivity while a sensitivity level settingof 0 corresponds to a minimum sensitivity setting (70 dB below maximumsensitivity). In accordance with the invention, the sensitivity settingis also a field in the memory of the portable ultrasonic detector sothat when the user presses the store button 85, the sensitivity levelsetting value is stored. In certain embodiments of the invention, theuser can also annotate data files that are stored, and by way of voicerecognition incorporate them into a final report.

In accordance with the invention, “Spin and Click™” controls are used toprovide an end user interface that is simple and intuitive. Withreference to FIG. 7, knob 72 acts as a cursor control. As knob 72 isclicked, the cursor moves in a set pattern around the display screen 82.If a “function field” is blinking, knob 72 is then spun to change thevalues within the function field. Once a function is selected, knob 72is then clicked to set the selected value.

In accordance with the preferred embodiment of the invention, multipleapplications can be displayed. In the preferred embodiment, 6applications can be displayed, i.e., GENERIC, LEAKS, STEAM TRAPS,VALVES, BEARINGS AND ELECTRICAL. Each application has two screens, i.e.,MAIN and STORAGE. In addition, the screens VALVES AND BEARINGS have anABCD SCREEN. The “Click” on knob 72 moves the “cursor” to “FIXED”positions on each screen. In certain embodiments, the number of controlsare minimized. In the preferred embodiment, two controls are used topermit the user to “navigate” through the various display screens, andchange multiple operational settings.

FIG. 10 is an illustration of an exemplary network of piping includingvalves that can be tested with the portable ultrasonic detector of thepresent invention. FIGS. 11(a) and 11(b) represent a flow chartillustrating the steps of the method of the invention. In accordancewith the invention, the method is implemented by performing a visualinspection of valve 117 (see FIG. 10) to confirm that it is closed or inthe off position, as indicated in step 1100. If the valve 117 is notclosed (step 1105), then the operator closes the valve, and proceeds tothe next step where a base line measurement for the valve 117 isestablished, as indicated in step 1110.

In accordance with the method of the invention, the ultrasound ismeasured at multiple points upstream and downstream from the valve. Inthe preferred embodiment, two upstream points A, B and two downstreampoints C, D are measured. With reference to FIG. 10, the first upstreammeasurement point A is at a distance located X times the pipe diameterfrom the valve. The second upstream measurement point B is locateddirectly upstream from the valve, approximately at the pipe fitting. Inaccordance with the method of the invention, the two downstreammeasurement points C, D are at a distance of equal relationship to theupstream test points, i.e., the first downstream measurement point C islocated directly downstream from the valve, approximately at the pipefitting, and the second downstream measurement point D is at a distancelocated X times the pipe diameter from the valve. In the preferredembodiment, X is six (6). In other words, the first measurements points(A upstream or D downstream) are located at a point that is 6 times thediameter of the pipe 120 away from the valve.

While touching a contact module to a measurement point to measure theultrasonic energy at the two upstream points, the sensitivity of thedual heterodyning circuit is adjusted by turning the rotary knob 72 onthe rear of the portable device so that the LCD 82 displays the dB valueof the ultrasonic measurements. The value of the ultrasound at theseinitial upstream points establishes the baseline measurements for thevalve 117. The ultrasonic measurement at the first and second upstreampoints should be close to each other. In some circumstances, the valueof the ultrasound at the second upstream measurement point can beslightly lower than the value of the ultrasound at the first upstreammeasurement point. In contemplated embodiments, the second measurementis performed without re-adjusting the sensitivity of the dual heterodynecircuit.

The first of two downstream test points C, D is then measured to obtainthe level of the ultrasound at this downstream test point C, asindicated in step 1115. The value of the ultrasound at the firstdownstream test point C is compared to the values of the ultrasound atthe upstream test points A, B, as indicated in step 1120.

The ultrasound at the second downstream test point D is measured toensure that no ultrasonic sound is emanating downstream from the valve117, as indicated in step 1130. The value of the ultrasound at the firstdownstream test point C is compared to the values of the ultrasound atthe second downstream test point D, as indicated in step 1140. If thevalue at test point D is less than the value at C, the valve is leaking.

If the value of the ultrasonic sound measured at the second downstreampoint D is greater than the value of the ultrasonic sound measured atthe first downstream point C, then an attempt should be made to “tuneout” or “shut off” this ultrasonic sound to obtain a proper test of thevalve, as indicated in step 1150. The ultrasonic sound may be “tunedout” or shut off by simply locating source of the sound, and takingmeasure to eliminate it, such as closing valve 115 in FIG. 10. When itis determined in step 1160 that it is not possible to tune out or shutoff a downstream structure borne ultrasound, it is necessary to locatethe source of the highest reading to determine its effect on the outcomeof the measurements. To accomplish this, an additional measurement ofthe ultrasound at a measurement point E is performed to assist inlocating/confirming the source of the ultrasound, as indicated in step1170. Hence, if it is determined in step 1180 that the value of theultrasound at the downstream point E is higher than the values of theupstream points A, B, then the valve 117 is leaking, and measures aretaken to correct the leak, such as by replacing the valve, as indicatedin step 1190. If in step 1180 it is found that the value of theultrasound at point E is lower than the value of the ultrasound at theupstream points, the valve is operating properly and does not need to bereplaced (step 1195).

If it is determined in step 1160 that it is possible to eliminate tuneout or shut off a downstream structure borne ultrasound, the value ofthe ultrasonic sound at the downstream point D is re-measured, asindicated in step 1200. A comparison of the values of the ultrasonicsound at the downstream points D and C is made, as indicated in step1210. If the value of the ultrasound at downstream point D is less thanthe value of the ultrasound at downstream point C, the valve is leakingand must be changed, as indicated in step 1220. On the other hand, ifthe value of the ultrasound at downstream point D is greater than thevalue of the ultrasound at downstream point C, the valve is not leakingand does not need to be changed, as indicated in step 1230.

If the values of the ultrasound at the downstream points C, D are closeto or lower than the values of the ultrasound at the upstream points A,B, then the valve 117 is not leaking, i.e., the valve is good, asindicated in step 1125 (see FIG. 11(a)).

In accordance with the invention, if the valve is working properly, thendownstream baseline decibel values are recorded and stored in memory forsubsequent comparisons to determine whether the valve is developing aleak. This is accomplished by re-measuring the ultrasonic energy at thedownstream locations and comparing the energy to the original downstreambaseline decibel values. If the ultrasonic energy at the re-measureddownstream locations is greater than the value of the downstreambaseline values, then the valve is developing a leak, and measures canbe taken to correct the problem, such as replacing the valve.

In an alternative embodiment of the invention, where it is not possibleto use multiple upstream and downstream test point, measurements areperformed immediately upstream from the valve. A measurement is thenperformed at a test point directly on the body of the valve. In thismanner, upstream values are obtained and compared with the subsequentdownstream valves to determine whether the valve is leaking or not.

In accordance with the contemplated embodiments of the invention, theultrasonic sound at the valve measurement points is recorded anddownloaded to a computer using spectrum analysis software. In thepreferred embodiment, the ultrasonic sound is digitized and stored onthe flash card 83 (see FIG. 4 and FIG. 6), and subsequently analyzedwith the spectrum analysis software. In accordance with this preferredembodiment, the spectrum analysis software is Spectralizerr™. Inalternative embodiments, the ultrasonic sound at the valve test pointsis recorded directly to a vibration analyzer to observe the amplitude ofthe ultrasonic signal at each measurement point.

The dual heterodyning circuit of the present invention provides anenhanced output spectrum. As a result, it is easier to determine whetherthe resonance is mechanical or electrical. In addition, faultfrequencies are also more easily detected. The enhanced signal outputprovides a lower signal-to-noise ratio, so as to increase the ease withwhich frequency components are analyzed. The method of the inventionpermits a user of the portable ultrasonic device to quickly and easilydetermine whether a valve is leaking or not

In addition, the method of the invention eliminates the unnecessaryreplacements of “good” valves, which can be expensive in certainenvironments, such as in a nuclear plant or on a ship, where the valvesare welded into place, by permitting a user to quickly and easilydetermine whether a valve is faulty.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

What is claimed is:
 1. A method for processing ultrasonic signals tolocate faulty components in a system having upstream and downstreamlocations using a portable ultrasonic measuring device, comprising thesteps of: performing a visual inspection of a device in the system toensure that the component is closed; measuring ultrasonic energy levelsat multiple upstream locations at fixed distances from the device toestablish baseline ultrasonic energy values for the component while thesystem is operational; measuring ultrasonic energy at locationsdownstream from the device; comparing a first measured downstreamultrasonic value to the baseline ultrasonic energy values; measuring asecond downstream ultrasonic energy if the first measured downstreamultrasonic energy value is greater than the baseline ultrasonic energyvalues; comparing the second measured downstream ultrasonic energy tothe first measured downstream ultrasonic energy; and removing adownstream source of ultrasonic energy if the second measured downstreamultrasonic energy is greater than the first measured downstreamultrasonic energy to determine whether the device is faulty.
 2. Themethod of claim 1, wherein said component is an on/off valve.
 3. Themethod of claim 1, further comprising the step of closing the downstreamsource of ultrasonic energy; and returning to said establishing step. 4.The method of claim 3, wherein the ultrasonic energy level at twoupstream locations is measured.
 5. The method of claim 4, wherein afirst upstream location is a predetermined distance from the componentand a second upstream location is directly at the component.
 6. Themethod of claim 5, wherein the predetermined distance is an integervalue multiplied by a diameter of a pipe in the system.
 7. The method ofclaim 6, wherein the integer is
 6. 8. The method of claim 1, whereinsaid establishing step is performed while adjusting a sensitivity levelof the portable ultrasonic measuring device; wherein the sensitivitylevel of the portable ultrasonic device is adjusted such that a dB valueof the ultrasonic energy is displayed on a display of the portableultrasonic device.
 9. The method of claim 8, wherein the sensitivity isadjusted by turning a knob located on a rear panel of the portableultrasonic measuring device, said knob also permitting navigationbetween various display screens on a display of the apparatus.
 10. Themethod of claim 1, wherein said step of measuring ultrasonic energy atdownstream locations comprises the steps of: measuring the ultrasonicenergy level at a first downstream location that is a predetermineddistance from the component; and measuring the ultrasonic energy levelat a second downstream location directly at the component.
 11. Themethod of claim 10, wherein the predetermined distance is an integervalue multiplied by a diameter of a pipe in the system.
 12. The methodof claim 11, wherein the integer is
 6. 13. The method of claim 1,further comprising the steps of: measuring ultrasonic energy at anadditional downstream point to locate an ultrasonic sound source. 14.The method of claim 1, further comprising the step of: recordingdownstream baseline decibel values; and storing the downstream baselinevalues in memory for comparisons with future downstream baseline valuesto determine whether the component is leaking.
 15. The method of claim14, further comprising the step of: re-measuring the downstream baselinedecibel values; retrieving the stored baseline decibel values from thememory; and comparing the retrieved baseline decibel values to there-measuring the downstream baseline decibel values; and replacing thecomponent if the re-measured downstream baseline decibel values aregreater than the retrieved baseline decibel values.